The present invention relates to apparatuses and methods for processing substrates such as semiconductor substrates for use in IC fabrication or panels (e.g., glass, plastic, or the like) for use in flat panel display applications. More particularly, the present invention relates to improved methods and apparatuses for moving components associated with processing a substrate.
Plasma processing systems have been around for some time. Over the years, plasma processing systems utilizing inductively coupled plasma sources, electron cyclotron resonance (ECR) sources, capacitive sources, and the like, have been introduced and employed to various degrees to process semiconductor substrates and display panels. In a typical plasma processing application, the processing source gases (such as the etchant gases or the deposition source gases) are introduced into a process chamber. Energy is then provided to ignite a plasma in the processing source gases. After the plasma is ignited, it is sustained with additional energy, which may be coupled to the plasma in various well-known ways, e.g., capacitively, inductively, through microwave, and the like. The plasma is then employed in a processing task, e.g., to selectively etch or deposit a film on the substrate.
During deposition, materials are deposited onto a substrate surface (such as the surface of a glass panel or a wafer). For example, deposited layers such as various forms of silicon, silicon dioxide, silicon nitride, metals and the like may be formed on the surface of the substrate. Conversely, etching may be employed to selectively remove materials from predefined areas on the substrate surface. For example, etched features such as vias, contacts, or trenches may be formed in the layers of the substrate.
In processing the substrates, one of the most important parameters that engineers strive to improve is process uniformity. As the term is employed herein, process uniformity refers to the uniformity across the surface of a substrate, the uniformity between different substrates processed in the same process chamber, and the uniformity between different substrates processed in different process chambers. If the process is highly uniform, for example, it is expected that the process rates at different points on the substrate, as well as process rates between different substrates in a production run, tend to be substantially equal. In either case, it is less likely that one area of the substrate will be unduly over-processed while other areas remain inadequately processed or that one substrate will be processed differently than another substrate. As can be appreciated, process uniformity is an important determinant of yield and therefore a high level of process uniformity tends to translate into lower costs for the manufacturer.
In many applications, process uniformity is difficult to maintain because of variations found in various parameters associated with processing a substrate. By way of example, the wafer area pressure (WAP), i.e., pressures surrounding the surface of the substrate, may fluctuate during a run of substrates because of temperature changes proximate the substrate. As is well known to those skilled in the art, if the WAP is higher for one substrate and lower for another substrate the desired processing performance between the substrates tends to be non-uniform. Additionally, if the WAP is higher across one area of the substrate and lower across another area of the substrate the desired processing performance across the surface of the substrate tends to be non-uniform.
One technique for controlling the WAP has been to provide a confinement ring inside the process chamber. The confinement ring is generally configured to surround the substrate in the active region, which is typically above the substrate to be processed. In this manner, the processing performed is more confined and therefore the WAP is more uniform. Although this technique works well for a number of applications, in many applications it would be desirable to provide a more controlled processing environment that can adaptively change to accommodate variations in the WAP during processing of a single substrate, during processing of a plurality of substrates in a production run or during processing in different chambers.
Recently, there have been some efforts to provide a moving confinement ring that can adjust the exhaust conductance and therefore the WAP. In this manner, the can be controlled to reduce variations that might occur during processing. One particular approach uses a cam system to move the confinement ring up and down between upper and lower electrodes. In this approach, a circular cam with varying levels on its surface is perpendicularly engaged with a plunger/spring mechanism that is connected to the confinement ring. As the cam turns, the plunger is moved up or down according to the different levels on surface of the cam, and as a result the confinement ring correspondingly moves up or down. Accordingly, the cam mechanism can be configured to control the gap between the confinement ring and lower electrodes so as to adjust the exhaust conductance and therefore the WAP in the active region above the substrate.
Although this technique generally works well, one problem is that the conventional cam approach provides only a limited range of pressure control, low sensitivity and low resolution (i.e., low precision). By way of example, the slope or level of the surface of the cam is limited by the plunger/cam interface because the plunger may get stuck if the slope is too large. As a result, the overall distance the plunger moves is restricted, which leads to the limited range of pressure control. Further, precise changes in the pressure during processing cannot be performed with the conventional cam approach. Further still, the plunger/cam interface may wear and the spring may loose springiness, both of which tend to reduce the reliability of the system.
Among the important issues to manufacturers is the cost of ownership of the processing tool, which includes, for example, the cost of acquiring and maintaining the system, the frequency of chamber cleaning required to maintain an acceptable level of processing performance, the longevity of the system components, and the like. Thus a desirable process is often one that strikes the right balance between the different cost-of-ownership and process parameters in such a way that results in a higher quality process at a lower cost. Further, as the features on the substrate become smaller and the process becomes more demanding (e.g., smaller critical dimensions, higher aspect ratios, faster throughput, and the like), engineers are constantly searching for new methods and apparatuses to achieve higher quality processing results at lower costs. In view of the foregoing, there is a need for improved methods and apparatuses for moving components (i.e., a confinement ring) associated with processing a substrate.
The invention relates, in one embodiment, to a plasma processing system for processing a substrate. The plasma processing system includes a component associated with processing the substrate. By way of example, the component may be a confinement ring or an electrode. The plasma processing system further includes a gear drive assembly for moving the component in a linear direction. In some embodiments the gear drive assembly is configured to move the confinement ring to control the pressure above the substrate. In other embodiments, the gear drive assembly is configured for moving a plurality of components. In a preferred embodiment, the gear drive assembly includes a first gear, a second gear and a positioning member. The first gear is configured for driving the second gear, and the second gear is configured for moving the positioning member in a linear direction. The positioning member is also fixed to the component such that when the positioning member is moved in the linear direction so is said component.
The invention relates, in another embodiment, to a plasma processing system for processing a substrate. The plasma processing system includes an electrode for generating an electric field inside a process chamber and a confinement ring for confining a plasma inside the process chamber. The plasma processing system further includes a gear drive assembly for moving the confinement ring or the electrode. The gear drive assembly includes at least a first gear, a second gear and a positioning member. The first gear is configured for driving the second gear, and the second gear is configured for moving the positioning member in a predetermined direction. The positioning member is fixed to the confinement ring or the electrode such that the confinement ring or the electrode is moved in the predetermined direction when the positioning member is moved by the second gear.
In some embodiments, the position of the confinement ring is configured to form a gap between the confinement ring and the substrate when the substrate is disposed within a process chamber for processing. The gap is configured for controlling the conductance of exhaust gases.
In some embodiments, the first gear and the second gear are rotatably supported by the process chamber. Further, the second gear is operatively engaged with the first gear. Further still, the second gear has an axis and a first threaded surface disposed at the axis. Additionally, the positioning member has a second threaded surface that is movably coupled to the first threaded surface of the second gear so as to provide movement in a linear direction.
In some embodiments, the gear drive assembly includes a driving arrangement for rotating the first gear. The driving arrangement includes a motor and a driving gear that is rotatably coupled to the motor. The driving gear is operatively engaged with the first gear, wherein when the motor rotates the driving gear, the driving gear drives the first gear to rotate, the first gear drives the second gear to rotate, the rotating second gear causing the positioning member to move in the linear direction.
In other embodiments, the gear drive assembly further includes a third gear and a second positioning member. The first gear is configured for driving the third gear. Further, the third gear is configured for moving the second positioning member in a predetermined direction. Further still, the second positioning member is fixed to the confinement ring or the electrode such that the confinement ring or the electrode is moved in the predetermined direction when the second positioning member is moved by the third gear. In a related embodiment, the gear drive assembly further includes a transfer gear for engaging and disengaging the second gear or third gear from the first gear, wherein when the second gear is engaged with the transfer gear, the first positioning member moves in the predetermined direction, and wherein when the third gear is engaged with the transfer gear, the second positioning member moves in the predetermined direction.
In some embodiments, the first gear, the second gear, the third gear and the transfer gear are rotatably supported by a process chamber. The transfer gear is operatively engaged with the first gear. The second gear has an axis and a first threaded surface disposed at the axis. The first positioning member has a second threaded surface that is movably coupled to the first threaded surface of the second gear so as to provide movement in a linear direction. The third gear has an axis and a first threaded surface disposed at the axis. The second positioning member has a second threaded surface that is movably coupled to the first threaded surface of the third gear so as to provide movement in a linear direction.
The invention relates, in another embodiment, to a linear drive assembly for moving a body associated with processing a substrate. The linear drive assembly includes a first gear and a second gear operatively engaged with the first gear. The linear drive assembly also includes a positioning member having a first portion and a second portion. The first portion is movably coupled to the second gear in a linear direction, and the second portion is fixed to the body. In some embodiments, the positioning member includes an externally threaded surface with a pitch and the second gear includes an internally threaded surface having an identical pitch to the pitch of the externally threaded surface. The externally threaded surface of the positioning member is rotatably mounted in the internally threaded surface of the second gear. In other embodiments, the positioning member is a linear gear (e.g. rack and pinion arrangement).
In some embodiments, the linear drive assembly includes a motor for driving the first gear. Additionally, the linear drive assembly includes a plurality of second gears and a plurality of positioning members. The second gears and the positioning members are symmetrically spaced apart about the periphery of the first gear. By way of example, the second gears are symmetrically spaced apart about the outer periphery of the first gear when external gears are used and the second gears are symmetrically spaced apart about the inner periphery of the first gear when internal gears (e.g., planetary gears) are used.
The linear drive assembly can be used in a wide variety of plasma processing systems including capacitively coupled, inductively coupled or ECR reactors. In a related embodiment, the linear drive assembly can be configured to move a confinement ring inside the process chamber of the plasma processing system. Additionally, the linear drive assembly can be configured to move an electrode inside or outside of a process chamber of the plasma processing system.